One electrophotographic color printer well known in the art is a tandem color laser printer equipped with four photosensitive drums to support the use of toner in the four colors yellow, magenta, cyan, and black. Each of four photosensitive drums corresponds to one of four developer cartridges for supplying developer to the corresponding photosensitive drum. One such tandem color laser printer includes a developing unit having a toner cartridge for accommodating toner for each color as developer cartridge. The toner cartridge has a toner accommodating section for accommodating fresh toner and a waste-toner accommodating section for accommodating waste toner.
The toner cartridge provided in the developing unit is formed with a lower toner supply port for supplying toner therethrough and with a recovery port for recovering waste toner therethrough. A toner discharging section of the waste-developer collecting section for conveying waste toner is fitted into the recovery port. Waste toner from the waste-developer collecting section is supplied to the waste-toner accommodating section through the recovery port.
Hence, if vibrations occur due to driving of the photosensitive drum during an image forming operation, the vibrations may be transmitted to the toner discharging section fitted in the recovery port of the toner cartridge, causing the toner discharging section to be damaged or causing waste toner to leak through a gap between the recovery port and the toner discharging section.